1. Field of the Invention
The present invention relates to a motor driving system for an electrically powered automotive vehicle of a kind utilizing a drive motor as a drive source for driving the automotive vehicle.
2. Description of Related Art
In the electrically powered automotive vehicle, or the electric vehicle for short, of the type utilizing a drive motor as a drive source for driving the automotive vehicle (such as disclosed in, for example, the patent document 1 listed below), failure of the drive motor and the failure of a controller used to control such drive motor are fatal in terms of the reliability. In driving the drive motor used in the electric vehicle, the timing at which the electric current is supplied to a coil wound around a stator of the drive motor, is controlled in dependence on the relative rotational angle between the stator and a rotor so that the efficiency thereof can be maximized. FIG. 5 of the accompanying drawing illustrates a schematic structure of the conventional motor drive system used in the electric vehicle of the type in which an in-wheel motor is built in a wheel support bearing assembly. In the case of the conventional motor drive system, in order to detect the relative rotational angle referred to above, an angle sensor 59 is provided in a portion of the drive motor.
In the case described above, for the angle sensor 59, a resolver or the like capable of accomplishing a high resolving angle sensing is used. More specifically, as the angle sensor for detecting the relative rotational angle, various structures have hitherto been suggested, including the structure in which a plurality of resolvers are incorporated and a plurality of output terminals are provided (such as disclosed in, for example, the patent document 2 listed below); the structure in which a plurality of detecting units (finite angle stators) comprising a resolver for the same rotor are arranged (such as disclosed in, for example, the patent document 3 listed below); and the structure in which a magnetic encoder and a magnetic sensor are utilized (such as disclosed in, for example, the patent document 4 listed below). Also, for those angle sensors, it may often occur that, as shown in FIG. 5, an angle calculating circuit 61 is provided outside a sensor body 60 for calculating the angle from an output signal of a sensor body 60.
[Patent Document 1] JP Laid-open Patent Publication No. 2008-168790
[Patent Document 2] JP Laid-open Patent Publication No. 2006-250864
[Patent Document 3] JP Laid-open Patent Publication No. 2008-309618
[Patent Document 4] JP Laid-open Patent Publication No. 2008-233069